| 摘要 |
PROBLEM TO BE SOLVED: To curtail a loss time at molding start-up and to prevent the scuffing between a peripheral ring and a mirror block by forming the ring and the block from different materials. SOLUTION: In order to make the thermal expansion coefficient of a peripheral ring 11 smaller than that of a mirror block 3 on the side of an antistamper arrangement, they are formed from different materials; for example, the ring 11 is formed by SUS 440S Revision, thermal expansion coefficient of about 10.3×10<-6> , and the block 3 is formed by SUS 420J2 Revision thermal expansion coefficient of 11.5×10<-6> . There is no need to change the structure of a disk substrate molding mold, and conventional technology is applicable. In this way, since a vent clearance S2 which is more than twice as large as a conventional clearance is obtained at the start of molding in which the temperature of the ring 11 is lower by about 10-30 deg.C than that of the block 3, the scuffing between them at the engagement can be prevented.
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